Even if your blood test results are in the normal range, they may not be optimal for your general health, physical and mental performance, and longevity. For many tests, values well within the normal range may be still be associated with an increased risk of mortality and certain diseases. This is why it is so important to establish optimal ranges for blood tests.

Read on to see why normal ranges can be unhelpful and misleading, why optimal ranges are so important, and which markers have normal ranges that could be doing more harm than good.

Why Normal Ranges Aren’t Always Helpful

Normal lab ranges are values that 95% of a healthy population falls into. They help doctors make diagnoses and treatment decisions. But they don’t tell you what’s optimal for your health and longevity.

Normal ranges don’t take into account large population research concerning the risks for disease and mortality. This research often reveals a much different range based on the lowest risk groups. However, most doctors don’t have the time to stay up to date on this research and apply it in their practice.

In some cases, normal ranges are created using populations that contain a significant number of unhealthy individuals, leading to ranges that don’t reflect a healthy population.

For these reasons, normal ranges for some tests aren’t helpful for the person that is trying to take control of their health or live the longest and healthiest life they can.

3 Markers With Misleading Normal Ranges

TSH (Thyroid-stimulating Hormone)

TSH is the hormone released by your pituitary gland that tells your thyroid to make the thyroid hormones, T3 and T4. The normal reference range for TSH is widely debated by researchers. Most labs have a range somewhere between 0.4 and 6 mIU/L, but many researchers have called for the upper limit to be decreased to between 2.5 and 3 mIU/L. One reason for this is that levels above 2.5 mIU/L are linked to an increased risk for developing an under-active thyroid (hypothyroidism) and even mortality [1, 2, 3, 4, 5].

Another reason is that the population used to create the original normal range contained a significant number of people with undiagnosed autoimmune thyroid disease. This led to higher TSH levels that don’t represent a truly healthy population. Indeed, recent studies have found that carefully-screened groups without thyroid dysfunction results in an upper limit between 2.1 and 3.7 mIU/L [6, 5, 7, 8, 9, 10].

As you can see, a TSH value within the normal range does not always mean your thyroid is functioning optimally. If you want to be truly healthy, you can’t wait for your results to fall outside the normal range to take action. You need to be proactive in keeping your TSH levels in a range with the lowest risk of developing hypothyroidism and other diseases.

Folate/Folic Acid (Vitamin B9)

Folate is another blood test with an unhelpful normal range. This vitamin is needed for DNA synthesis, red blood cell maturation, cell growth, and proper brain development. It also helps decrease homocysteine, a molecule linked to heart disease [11, 12, 13, 14].

Most labs use a lower limit of 3 ng/mL to diagnose a folate deficiency, but researchers have called for the limit to be raised to as high as 13 ng/mL [15].

What levels should you aim for if you want to be optimal in terms of health and longevity? Research points to an optimal lower limit much higher than the established one.

For example, in a study of 29,000 people, levels below 17 ng/mL were associated with an increased risk of death [16].

Another study of 1,921 people found that the lowest risk of heart disease was seen in people with levels above 9.6 ng/mL [17].

Levels above 11.3 ng/mL were associated with a 39% reduced risk of lung cancer compared to levels below 7 ng/mL [18].

This shows that the optimal lower limit for folate is much higher than the current normal lower limit, and is another reason why you shouldn’t rely on the established normal range to determine if your levels are truly healthy.


The normal upper limit for triglycerides is 150 mg/dL. But there is a lot of research showing that the upper limit should be much lower.

When scientists reviewed 61 studies with 726,030 people, levels below 90 mg/dL were associated with the lowest risk of mortality. Another meta-analysis of 13,957 people found that levels below 88 mg/dL were linked to the lowest mortality risk [19, 20].

In addition, levels below 88 mg/dL are associated with the lowest risk of heart attack. Levels above this magnify the risk of heart attack when cholesterol levels are also high. In other words, high cholesterol levels become much more dangerous when they are accompanied by triglyceride levels above 88 mg/dL [21].

Triglycerides above 90 mg/dL also increase the risk of developing diabetes [22].

As you can see, for markers like this one, relying on normal ranges can be dangerous. It can give you a false sense of security and prevent you from taking steps to improve your levels.

Normal Lab Values But Feel Like Something Is Off?

LabTestAnalyzer helps you make sense of your lab results. It informs you which labs are not in the optimal range and gives you guidance about how to get them to optimal. It also allows you to track your labs over time. No need to do thousands of hours of research on what to make of your lab tests.

LabTestAnalyzer is a sister company of SelfHacked. The proceeds from your purchase of this product are reinvested into our research and development, in order to serve you better. Thank you for your support.

About the Author

Will Hunter

BA (Psychology)
Will received his BA in Psychology from the University of California, Los Angeles. 
Will's main passion is learning how to optimize physical and mental performance through diet, supplement, and lifestyle interventions. He focuses on systems thinking to leverage technology and information and help you get the most out of your body and brain.

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